Bamboo skewers stronger than pocket holes? Dowels vs. screws.

Testing right angle joints using screws into the end grain, pocket holes, and different size of dowels.

[@wessss]

Might be a neat idea to test dowells of various lengths. See where the benefit of longer dowells, if it exists, meets diminishing returns.

[@richbuilds_com]

Gut feeling is its exponential, not linear.

[@richbuilds_com]

ie. longer lengths get exponentially harder to pull out

[@Paremo_]

And washers! How big do I need to make 'em to rip out the threads? Does a flat-on-the-bottom washerhead suffice?

[@Uncephalized]

You'll get a linear relationship as glue surface increases proportionally to length. Then there will be a hard limit at the breaking strength of the dowel, which depends on its diameter.

[@davidswanson5669]

Is there such thing as a spiral fluted dowel? Essentially a screw-looking dowel, where insertion is still done via press-fit just like all other dowels, rather than needing to screw them into place. Also the spiral flute wouldn’t have a tight screw pattern, but rather an elongated spiral, otherwise failure would be too easy.

[@samTollefson]

Thank you, Matthias! I use quite a few bamboo dowels because I have them and they are cheap. One thing I have noticed, some of them have a burnished almost waxy surface feel to them. I don't know if it is a substance in the bamboo or a result of the dowel-making process or both, but I feel it may hinder the glue from fully penetrating the surface of the dowel, on those, I give the full-length dowel a light sanding with 220 paper before cutting them to length, I don't know if this helps though.

[@matthiaswandel]

I suspect its burnishing from how they were made. I gave my dowels and skewers a very light sanding before using them

[@RubenKelevra]

That's part of the production process: It's when the cutter gets fairly hot that the wood may loose a bit of resin in the process (like it's cooking off). You can sometimes see this if you cut wood as well, then you get a glossy very flat surface instead of a normal cut (and shortly after you see burn marks).

[@samTollefson]

@@RubenKelevra Thank You, that is much how I imagined it happening. Some parts of the bamboo may have less resin which would explain why some have a dry woody-like appearance, whereas some others containing more resin would have the burnished areas with a slight sheen. That being the case perhaps using a solvent would be a better prep for glueing than sanding?

[@GraemePayne1967Marine]

I have been using small bamboo skewers - the ones you can get at a grocery store - as dowels in small projects for a long time. I find them useful especially when joining thin pieces of wood side by side. They work well for me. But I don't have all of the quantitative test equipment that you do, so I have no actual data to share.

[@justmakeit2849]

I will have to try those. At present, I don't use dowels on thin pieces

[@IMDunn-oy9cd]

While one method may be marginally stronger than another, all of these tests demonstrate to me that any of them are adequate for my needs.

[@ChrisUhlik]

This is my favorite type of Matthias video. Full of real data about real world building strategies. Super valuable stuff!

[@marcelg1157]

The endgrain VS longgrain screw holding power is as surprising as the endgrain to endgrain glue strenght in one of your earlier test😉

[@gbeckowski]

Great video. It would be interesting to see a "stress-strain", actually force-displacement, diagram for each joint. Then you could get a sense of the failure mode of each, at least from a brittle/plastic mode.

[@pefu512]

I would like to know, how much would putting a suitable sized washer beneath the screw head prevent the screw head from sinking in and such increasing the strength of the joint. The result of end grain versus cross grain was indeed somewhat surprising.

[@davefoc]

I used four inch screws driven through the stiles into the rails as my first attempt at fixing some old windows. I used the washer under the screw technique and I was sure that it was better than using just a screw. I abandoned the screw for the dowel technique because I thought the dowel was a better long term fix. Even with out the issue of the screw head working like a wedge there is still the issue of the screw damaging the wood over time because racking from the wind load.

[@Art-is-craft]

@@davefoc Main weakness of dowels is that they expand and then contract. Not an issue when the force is generated across the joint but becomes an issue then the force pulls the joint.

[@andrewgalbreath2101]

I'd imagine the fluting adds a good amount of surface area without increasing the radius, which seems especially important bc the dowels seem to pull out rather than fail themselves

[@joelhollingsworth2374]

My theory is they allow glue to remain during installation, preventing the joint from becoming glue-starved; either way, it shouldn't be too hard to just run a screw up and down a dowel to add some fluting.

[@MattMcConaha]

My thought was that the fluting allows for a tight surface contact for gluing. The high spots of the fluting are able to be slightly larger diameter than the hole, and deform easily to fit the hole. For a solid dowel, you need to be a lot more precise with the hole size or else the dowel either won't be very snug or won't fit.

[@rcdogmanduh4440]

Or the flutes allow the air in the hole to vent when pushing dowel in?

[@paulbalegend]

@@joelhollingsworth2374 yeah i agree with this assessment. there's just not much glue left in the mating surface area after pushing a standard dowel in.

[@johnhandshake4460]

very interesting bonus test at the end... I didn't expect the endgrain to do so well. thanks!

[@Laundry_Hamper]

As a bonus, flush-sanded bamboo skewer dowels look brilliant

[@microwave221]

Thanks for teaching me not to shy away from screws in endgrain anymore, l never would have expected that to work so well

[@F0XD1E]

Did he mention what pilot hole size he used? That could be important. I think he had done a previous test on that but can't remember if that included end grain.

[@microwave221]

@@F0XD1E l don't think he mentioned it this time, but usually you wanna go for about the minor thread diameter, or the thickness of the core of the screw between the ridges

[@JonnyDIY]

Very interesting results Matthias, thank you for sharing. I enjoyed this one 🙌💕👍

[@AvinashArora0]

Thank you so much for this! This is exactly the additional testing I wanted to see after your last tests!!

[@weldabar]

This is good information. I would have never guessed that dowels would perform this well. And I like using dowels over screws for a lot of projects, but not all.

[@bexpi7100]

Would be interesting to see if the relationship between screw strength in end gain vs cross grain stays about the same across different types of wood. Also would be interesting to quantify that comparison in plywood since I'd expect screwing into the side of plywood to be significantly weaker than the other direction.

[@stephanmunro3658]

Hello Matthias, thanks for video, Super video with stats, it blows my mind the things you able to do, either machine building or testing. Thank you, very informative. Regards

[@tomdenny8507]

Thank you for this video. I always find your activities fascinating.

[@PeranMe]

BEAUTIFUL jig, man! Excellent job!

[@kevinetheridge6153]

I really enjoyed this video. I enjoy dowels, but sometimes had the thought that they weren’t as strong holding as screws, for whatever reason. This really did provide some useful data for me. Thanks!

[@DconBlueZ]

Thanks for the video, always enjoy watching!

[@IstasPumaNevada]

I always love seeing these methodical tests.

[@davefoc]

My experience with repairing wood windows: 1. Two inch long fluted dowels about thirty years old. Mostly the glue from 1976 had failed long before I was working on the windows. 2. Miscellaneous kludge screws to try to fix the failed dowel joints: The dry wall screws were rusted through (the windows were at the ocean) and the zinc plated screws didn't do much better. I also thought that there was a failure mode where the rail/stile joint failed from the screw working against the wood over time from wind loading. 3. 7/16 inch dowels through the stiles into the rails from the outside with titebond glue: As near as I could tell this was a permanent fix in the sense that something else was probably going to fail in the window before the rail/stile joint. I saw no reason for the fanciness of hiding the dowels inside the joint I just drilled a hole through the stile into the rail with the window clamped together. For awhile I was concerned that I wasn't using a fluted dowel. I doubt that was an issue. I put glue on the dowel and into the hole (I used an acid brush to make sure the inside of the dowel hole was thoroughly coated). As an aside I thought about doing the kind of testing that was done in this video. I never did but I thought the testing in this video vindicated my choice of window repair method. One thing though, I could just pull the old windows apart because the original joints had failed. I don't think the guy who tries to repair the windows I fixed will be able to tear the joints apart in 30 years.

[@SeahawkSailor]

Thanks Matthias. This was a really great test to see!

[@Retanaru]

I'm here to say I really appreciated the short intro to action. 26 seconds on a 9 minute video is impressive.

[@Liofa73]

Perhaps it's time to buy a clip-on displacement gauge allowing you to plot force vs displacement. It would be nice to track the drops in force and jumps in displacement, you can then associate them with what you see and hear during your tests. Some other nice data to be had from such graphs, work done etc. A bit of extra nerdy fun.

[@UberAlphaSirus]

IRC digital calipers have serial interface pads in the baterry compartment

[@paradiselost9946]

i like this. simple, direct, and conclusive. worth the time dealing with clamps and jigs and boring holes...

[@seanseoltoir]

Back in the old days, when we were adding a wall to a concrete slab (such as when changing an open carport into an enclosed garage or additional family room), we would use a hand chisel type star drill to put a hole in the concrete and then pound a peg of wood into the hole. We would then drill pilot hole into it and use that the mark the location of the hole for the 2x4 baseplate for the wall. Then we would use a lag screw to attach the baseplate to the peg and thus to the concrete. Later on, we started using lead and/or zinc inserts into the holes, but still lag screws. It would be interesting to see how the strength of those old solutions compare to the modern concrete fasteners.

[@kerrykrishna]

Mathias, I am really enjoying all the new vids!

[@ddutton0]

These videos are always so great!

[@vandenpiaff]

Thankyou very much for an very informative and useful video. I am really enjoying those videos. Thanks Matthias, Best to you and your family from Denmark

[@wiseoldfool]

Lovely bedtime story! Thanks Matthias.

[@Gefionius]

Awesome! Thank you for all the hard work

[@jacohop]

You’re slowly creating a wonderfully valuable database that I’m sure will end up being cross-referenced exponentially over time

[@XJWill1]

I wonder how 2 or 3 bamboo skewers would compare to one 3/8 dowel pin, if you space the skewers tightly so they do not take up a lot more volume than the dowel pins.

[@thejo6331]

These are so nifty! Thanks for making these!

[@johnmayer5920]

I would’ve liked to have seen you test the pocket hole screws in the same orientation as the other wood screws, as I don’t think the heads would’ve pulled in as far and maybe held just as well or better.

[@dlc3000]

That was my first thought as well. Matthias speculated on the wedge head of the regular screws. The pocket screws have a flat head where it contacts the wood. I wonder if the flat head would avoid the sub-200 joint separation?

[@tracybowling1156]

I went in thinking that- of course screws would win. These tests were quite a surprise! I absolutely love a good experiment!

[@Trooper266]

An additional parameter of interest could be the rigidity of each joint, which, depending on the application, might be even more important than the tensile strength.

[@rogerdudra178]

Greetings from the BIG SKY. A good analysis of screwing around.

[@johnhawkinson]

This makes me wonder about angles! Toenailing in actual nails at 30°. Or even skew(er)ing the skewers and dowels at angles so they are not in-line with the pulling force.

[@olestampevestergaard4746]

I love watching you break stuff 😊

[@salimufari]

Very solid experimentation with large sample sizes. Very good Science sir.

[@DingusSquatfordJr.]

Your experiment and testing are inspiring to engineering students.

[@cartmanrlsusall]

This was a good video and answered a lot of questions

[@jeffreywhitmoyer860]

The instant you have visual separation could be considered the yield point. In the case of the screw heads the wood beneath the seat is yielding to the load. Up to that point the wood is probably elastic, after that point the screw hole undergoes plastic deformation. Interestingly, a lot of people think in terms of ultimate strength when the component is often no longer useful after yield. The beauty of ultimate strength is that it provides a little margin after yield and before ultimate is achieved. That provides an opportunity to avoid sudden catastrophic failure. Interesting set of tests.

[@viktorshutov]

Thank you, this is useful! No legends and fairytales - just raw tests and analysis.

[@MKRM27]

I don’t see it as that useful. Not many joints are stressed in this way.

[@viktorshutov]

@@MKRM27 normally something bends or tips, and in this moment corner of wood piece is pushing to wood while screw or dowel is being pulled out of wood. Don't you think so?

[@carlgradolph9676]

Being no engineer, I can't comment on your test methodology, but based on videos of yours I watched a long time ago, I have been using wood-dowel joinery on most of my simple projects, and these have all held up way better than I would have expected, given my clumsy techniques and the crappy pallet or salvage wood I tend to use. This video only reinforces what you have been showing your viewers for ages. One obvious point: Few people make their own screws, but anybody can make their own dowels, using scraps that normally would just be thrown away.

[@cartmanrlsusall]

That is why dowel joints can be repaired and screws make such a huge mess when they fail or get overstressed

[@kenharrison3364]

I love these tests, thanks. Great information, I’d like to see a comparison with cross wise pressures, but that may be more of a measure of the wood and not the medium of attachment.

[@matthewphelps5136]

Mattias's hatred of pocket holes will never die. I can't say I blame him. I hardly use them.

[@johndoe6032]

Interesting results. I like using dowels instead of screws, but they take a little more work to use for joining, and I actually assumed screws were stronger. I wonder what the results would be with a more sheering force on the fastener; turning your test pieces sideways and applying opposing forces on each piece being joined.

[@MKRM27]

A sheer force would be much more relevant

[@Traqr]

This is a discussion that comes up all the time in these tests, and it depends. This is more like the top connection where a seat meets the back of a chair, so it has relevance. As this test showed, stronger connectors (screws) don't always mean stronger joints if they tear through the substrate, which is why the strongest joints are the ones that distribute the forces the most (dowels, box joints, tenons, etc.) That holds for both tension and shear. Given the results, I'm now curious about a "pocket screw" with the wide, flat washer head recessed slightly into the surface but driven up into the endgrain like the other screws. They tend to be skinny so I don't think I'd trust the shear strength, but it would reduce the splitting that caused these screws to fail. Also, he could have run a couple of dowels, skewers, or splines across his samples to reinforce the cheeks, bit that's a note for the next tester.

[@weldabar]

Good design would minimize sideways forces. For example shelving would be housed in a dado and the screw could keep the shelf in the dado. You would never design a piece where a sideways force on the screw itself could be the failure point. (and by "never" I mean someone is going to do it, but it shouldn't be done).

[@BloodyMobile]

It's impressive that the simplest dowel held up longer, and that the screw instead gave a lot of "heads up" that it _is_ going to fail, but failed completely different instead.

[@DullPoints]

I'm loving this stuff. I feel like it's building towards something that would make for a catchy thumbnail "proven: best furniture ever made"

[@ActuallySettle]

Matthias' pull out game is crazy

[@sixtofive]

Interesting results!

[@mastheadmike]

This was like my old strength of materials labs..without having to write my own lab reports. Loved it.

[@kaf2303]

Very nice analysis! Thanks

[@MartinKL]

Great video. I love the scientific evidence vs. hearsay.

[@TimothyHall13]

Up next: multiple dowels/screws. This is invaluable testing. Thanks for sharing.

[@darthrevanakc]

Thank you for doing this. I would love to see how lag bolts or construction screws would hold up (thinking GRK fasteners). I’ve considered using them and then covering the hole with a dowel for an easy joint.

[@Vikingwerk]

I saw a video recently where someone said that the commercial dowel pins are compressed, so that when you add glue and assemble, the moisture in the glue causes them to re-expand a bit, locking them in the hole tighter. I’d never heard that before, and have no idea if it’s true. I don’t have any on hand, but I guess you could test it by lightly wetting one and seeing if it did expand.

[@ScottBishop6]

Thanks for the good testing/video, I always enjoy finding out what works best. I have seen dozens of KZbins for making your own dowels, but there was one I really liked. You just use a thread cutting die and spin the prepared stock through it. With a complete die set you can make any size dowel you want, and they come out with good gluing surfaces. I wonder how they would work in you test jig?

[@torque8899]

Love these tests, I’m always telling my brother that screws hold better than you’d believe they would. Many a house is built with screws and nails, not everything has to be proper joinery if your in a rush.

[@superdau]

I always wanted to know how large the difference between screws crossgrain and endgrain is. If I had to guess, I would have said endgrain has half the holding strength (not measured anything, just had a feeling that endgrain fails proportionally more often). Good to see that they are way closer than I thought. So the endgrain failures were more likely due to where they were used (butt joints, which pretty much always are like a lever) than the strength of the connection itself. Also good to see that drywall screws work almost as well as wood screws (and are even more consistent over grain directions). They are cheap and I have a lot of them left from building drywalls during a renovation.

[@thedevilinthecircuit1414]

Used to be you could get spiral-fluted dowels at most builder's supply places. These days they're all straight fluted. I'm sure the spiral type is still available...and probably makes for a stronger glue joint.

[@tiporari]

I use drywall screws for lots of quick projects. They are cheap as chips, and very strong.

[@alans1816]

Moisture cycling should hurt the strength of crossgrain screws more than that of endgrain screws, since expansion and contraction should stress some threads more than others. Into endgrain screws can be as long as you like. Hoadley specifies half the pullout strength per length of screw into endgrain vs sidegrain. I wonder if the difference with your results is hardwood vs softwood.

[@reidflemingworldstoughestm1394]

Ya finally splurged and got the TB III. Love that green cap stuff.

[@proteanwanderer]

Thanks for looking at this often asked question. Very appreciated! Can you address pocket hole screws with the various common wood glues? (Titebond, Elmer's, maybe a 5 minute epoxy, etc?) Can you show us how your test platform is set up?

[@Korgon2013]

These are great videos

[@vanshankguitars]

Any thoughts of trying with pan head screws? I'm all my years of joining wood with screws, I found pan head screws to be best.

[@imqqmi]

Would be interesting to test two screws at different angles, that way pulling out doesn't rely on the screw heads as much. And pilot holes vs no pilot holes.

[@coffeewithalexander]

This would be interesting to see with different types of screws. The wedge shape of many seems like a point of potential compromise to me, so, in appropriate applications, like butt joints, i use countersunk cabinet screws, which have an integral washer. While my preference is generally dowel joints, i am convinced that an appropriate screw style can be technically superior in some applications.

[@nunyabidness3075]

Did you try screws with glue? What glue and metal combo would work best I wonder? In the end, these tests often ignore the importance of what the application actually calls for, but they are still fun and informative.

[@JoergGebhard]

Wonderful as always. So takeaways for me is: use two screws instead of one dowel and screw in endgrain work!

[@Hoaxer51]

On those tests where the dowels were pulling through, could you test some with the dowel cross pinned, maybe with a bamboo pin?

[@Dan-qi4np]

I'd be curious to see the impact of screwing/doweling into quartersawn vs. plain sawn vs. rift sawn. Does the ring orientation of the wood make a difference (especially in the screw head pull-thru)?

[@AngryArmadillo]

Would be interesting to plot the force curve over time for each sample, and then maybe overlay them all together. That would help show the different failure modes. Not sure if you’re logging that data.

[@maililistaalterego]

I wish you could test my favorite: 2.5mm "bamboo nails" (bbq skewers). They are a really easy method of reinforcing rabbet joined boxes for example. But I'm not sure how much they provide strength, especially if the rabbet is already glued.

[@redmysterium]

I have been using little coin magnets in plenty of recent projects. Sometimes magnets that attract to metal and also magnet to magnet. I would be very interested in seeing some testing on those. Especially what little air gaps might do to the final pull strength. I can't always get things perfect and have wondered about eh seemingly exponential falloff with magnets.

[@paradiselost9946]

air gaps... bad news. iirc, its a cubic inverse ratio. its really hard to set anything ins tyone with magnets as its geometry based, material based... but air gaps are just bad all round. try to use pots if possible. bit costly but well worth it. shields the field externally so no nasty stuff happens, and the field is concentrated between those two iron poles. can make them though? like magnetic door latches were always a simple ferrite between two iron plates or keepers, set back from the outer edge (gives two defined poles, and magnetic "junk" doesnt get in the way so much...), and the latch is a simple iron plate to bridge the gap. no air gap when latched. keep all the field in the iron where it wants to flow. rather than use one pole only, think of "closing the loop" instead. far more efficient. and soft iron lets you manipulate where the field is. magnets LIKE to be shorted out with iron. not just stuck on one pole but shorted out.

[@redmysterium]

Wow, thanks for your suggestions. So pots are like the door latch magnets? I had never heard that. I never thought about shorting out a magnet either.@@paradiselost9946

[@zukjeff]

excellent content and presentation. I would like to see the bamboo in shear when it is used as a scroll pin. i use this method where i don't want metal fasteners or i want the pin to pull a joint together using a taper.

[@helion6884]

These tests are awesome. I enjoy seeing how different methods behave. I am curious what the failure modes are for real world furniture and what the thresholds of force on them are. I suspect short peaks through racking are a big one and that degrading materials from time and moisture changes are the bigger ones. My suspicion is that in real use for most furniture builds you hit diminishing returns well before getting to optimal raw strength of the fastening methods

[@SandyMasquith]

Thank you for doing all this testing and video-making. This information is invaluable to the carpenter and woodworker. I wonder if you might be able to do some testing with hardwoods? I feel that the hardwoods (walnut, hard maple, cherry, hickory, oak) might be able to withstand the head pulling through better than softwoods. The other consideration is that furniture typically isn't made with softwoods. To be honest, most fine furniture is made with loose tennons or dowels instead of screws, but that's a whole other thing. I really am curious to see how hardwoods can resist pulling the head of the screw through them. I can send you some sample hickory and walnut. I might be able to send some cherry as well. I don't really have any oak or hard maple though.

[@sevenismy]

It would be nice to see the performance of woodscrews with washers.

[@G4m1c]

That would be very similar (or identical?) to the test where he pulls directly on the screw in end grain.

[@fookingsog]

Or just use Lath Screws!!!🙄

[@sevenismy]

Just that how big the washer has to be, so it outperforms the threads in the end grain. And also when you bore a bigger hole for the washer+head how big is the negative impact?

[@EMTdrummer]

I love these tests... lots or woodworking (and construction for that matter) is based on folklore... I often wonder which type of force is more typical on furniture fails... sheer, torque, pullout, etc...

[@taba1950]

The amount deformation before the failure can also be a data point

[@crushvapor1147]

Very interesting, I wish the pocket holes would have held up better. I'm curious as to whether screws plus glue(or dowels) is a stronger joint than adding the strength of each one separately. Synergy?

[@wardprocter2371]

Would like to see a comparison of two or more bamboo skewers vs. a single 5/16 or 3/8 dowel.

[@GreenAppelPie]

I’d like to see sheering strength test with dowels, joinery, nails nails and those common gold screws from the big box stores

[@DaveChurchill]

Why do you think the fluting on the dowels helps? Extra glue surface area?

[@omegaflameZ]

I'd be curious how much pinning a 3/8" dowel with a bamboo skewer, i.e., at each end drill a hole equivalent to the skewer size through the dowel perpendicular to the direction of force and glue it in, effects the results. I've seen this suggested for joints where you want some mechanical fastening even if the glue joint on a dowel or biscuit/domino/loose-tenon fails.

[@pshadyyx]

Thank you for this test. Would you think a similar test with hardwoods (beech, maple, etc.) could yield different results and consider doing one?

[@matthiaswandel]

yes, different results. But if you build with hardwood, you usually don't just screw it together anyway

[@timfoster5043]

Now I'm wondering about stats for different kinds of wood. I think you used soft pine on those. I wonder how oak would hold up on, say, end-grain vs cross-grain screws.

[@JasonJonesoriginal]

Another fun thing to test would be wedges in things like axe handles. Which ones fail sooner? Very curious to know!

[@artswri]

I always watch till the end... And always learn something new but more importantly, something _useful_!

[@washoecreative595]

Some time ago I switched to using 3/8 inch dowels for shop furniture joinery (benches and such). I don’t find screws any easier to use than dowels. Just clamp up your assembly, drill your holes, pound in your dowels, trim them down when the glue is dry. Simple. And apparently plenty strong. The practice of putting screws deep into counterbores and then covering the heads with dowels for cosmetic purposes mystifies me: why not just use dowels in the first place?

[@AtypicalADultHooD]

I wonder how much of a difference it makes to alternatively angle the fasteners forming a series of Vs along the joined edge. It's commonly done with wire nails, but treenails and screws might benefit from it as well.

[@joshuacrooke2913]

I would be interested in seeing the results of the pocket hole joint with glue and screws.

[@awldune]

I would be interested to see a test with side load / racking force rather than pulling straight out. I suspect that screws in general would do worse?